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Keeping you informed about the TecEco cement project.   Issue 34,   15th May 2004

Another Research Program Underway in the UK.

I received the good news that the research project titled "Waste minimisation through Sustainable Magnesium Oxide Cement Products" has been funded by the Engineering and Physical Sciences Research Council (EPSRC) in the UK.

The project is a collaboration between Dr Abir Al-Tabaa, Dr Janet Lees and Dr Bill Clegg of Cambridge university and Dr Chris Cheesman from Imperial College, London. Dr Abir Al Tabaa is the overall principal investigator.

Cambridge university will be employing a post-doctoral research associate for 3 years and Imperial College will be appointing a PhD student for the same length of time. Both universities will both be shortly advertising to fill these positions.

A summary of the project follows:

Waste Minimisation through Sustainable Magnesium Oxide Cement Products

Cement and cementitious building products consume vast quantities of natural resources and constitute a large proportion of construction, demolition and other industrial waste. There is therefore an urgent need for innovative, creative, cost-effective and sustainable approaches to reduce the tremendous environmental impact of conventional cement-based technology and applications. One developmental area with significant potential has been the inclusion of wastes and industrial by-products in building materials. However, in spite of clear environmental and cost advantages, work in this area has been limited. A major problem with the incorporation of waste materials into new products is that they usually suffer from a lack of homogeneity, sometimes include contamination and are generally seen as producing a lower quality product. Hence, an improvement of the engineering behaviour of any new cementitious products containing waste, and in particular their durability and waste binding capability, is essential for their commercial viability. The recent emergence of magnesium oxide cements (MgO cements) such as the much ‘Eco-cement’ provides a unique opportunity to develop durable high quality novel cement-based construction products that incorporate a large proportion of waste materials. MgO cement uses ‘reactive’ magnesia that is manufactured at much lower temperatures than Portland cement (PC), contains a large proportion of by-product pozzolans, is more recyclable than PC and is expected to provide an improved durability and to have a high propensity for binding with waste materials. This project proposes to investigate the fundamental properties and behaviour of MgO cement formulations and MgO cement-waste mixes and their potential application in the development of construction products that contain large quantities of waste yet have either comparable or even improved durability and/or reduced leachability when compared to PC-based products.

Investigators

The project brings together researchers from Cambridge University, from both the Departments of Engineering and Materials Science and Metallurgy, and Imperial College London, Department of Civil and Environmental Engineering, all three departments were rated 5* in RAE2001, and from the Departments of Civil and Environmental Engineering and Architecture at MIT. This strong international multi-disciplinary team has complementary expertise in the various areas covered in the project.

Dr Abir Al-Tabbaa is the Principal Investigator, coordinator and manager of the project. She is a Senior Lecturer in Geotechnical and Environmental Engineering at the University of Cambridge and is a Chartered Engineer. She has sixteen years research experience in sustainable waste reuse and contaminated land remediation. Her research work has included the use of a wide range of wastes in civil and environmental engineering applications including in-ground barriers and novel binders for soil improvement and waste immobilisation1,2. Prior to embarking on her academic career Dr Al-Tabbaa was a geotechnical engineer with ARUP Geotechnics in London involved in the design and construction of major projects. She is the principal investigator of £230k projects (GR/N03280, GR/N03297, GR/R38033) on stabilisation/solidification treatments and the durability and long-term performance of cement-treated contaminated and uncontaminated soils. This involved the experimental and numerical modelling of accelerated ageing of these materials. She has been awarded the 2003 Reed and Mallik medal by the Institution of Civil Engineers for this work2. She is a main collaborator in the £1.92M consortium SUBR:IM (Sustainable Urban Brownfield Regeneration: Integrated Management, GR/S18809). She has supervised over 30 research students and produced over 60 publications. She is a Research Manager within the Mini-Waste Faraday Partnership and was a main player in the establishment of the Partnership. She is currently supervising PhD projects on the applicability of a wide range of novel materials in novel grouts, the immobilisation of oil drill cuttings, the stabilisation of peat and the accelerated carbonation behaviour of cement-based products.

Dr Janet Lees is a University Lecturer in Structural Engineering at the University of Cambridge and is a Chartered Engineer. Before embarking on a career in research, she spent three years in Industry working both for a Consultant and for a Contractor. For the past nine years she has been carrying out research into the use of advanced materials in construction and concrete applications. A particular area of interest has been the field of strengthening and repair of existing concrete structures3(GR/S55101). She has worked with colleagues in the UK, US, Switzerland and Japan and is running a number of ongoing projects in collaboration with industry and other international laboratories. Her recent work on the development of durable carbon fibre reinforced polymer prestressed concrete structures4 for offshore applications is the subject of an ongoing international collaboration with North Carolina State University (GR/S29669). Additional research interests include composite pipeline technology (GR/N20768, GR/R09770) and the use of recycled materials in concrete. She is also a member of the EPSRC Network on Advanced Polymeric Composites for Structural Applications in Construction (CoSACNET). She has supervised 14 research students and has written 25 publications. She has received a 2002 Royal Society Brian Mercer Innovation Postdoctoral Award to undertake research on novel measurement systems for the long-term performance of concrete with external fibre reinforced polymer reinforcement.

Dr Chris Cheeseman is a Senior Lecturer in Waste Management in the Department of Civil and Environmental Engineering at Imperial College London and member of the Chartered Institute of Wastes Management. EPSRC funded research (GR/M51444) investigated the sintering properties of municipal solid waste incinerator bottom ash and the production of lightweight aggregate. The project demonstrated the potential for producing LWA containing significant proportions of IBA with key properties comparable to commercially available products5. Research has also investigated sewage sludge ash from fluidised bed incineration. Results indicate the potential for manufacturing high quality lightweight aggregate using simple processing and low temperature sintering. Lignite coal fly ash from the 'Nikola Tesla' power plant in Serbia has been characterised and sintered to form monolithic ceramic materials in collaborative work with the University of Belgrade (Royal Society grant). Low-grade PFA from Hong Kong, unsuitable for use in construction because of high residual carbon content and coarse particle size has also been used to produce ceramic materials. Recently completed EPSRC funded work (GR/M L64522/01) investigated microbial influenced degradation of solidified waste and the characterisation of environmentally exposed cement-based stabilised/solidifies industrial wastes.

Dr Bill Clegg is a Reader in Ceramics in the Department of Materials Science and Metallurgy at the University of Cambridge. Before joining Cambridge in 1992, he worked at I.C.I., Runcorn Heath in the group of J.D. Birchall working on processing of ceramics and high strength cements. At Cambridge he has pioneered the use of layered ceramic structures as a cheap, cost-effective means of toughening a ceramic, particularly in thermal shock. Other interests have included crack deflection, the fracture of permeable materials and, more recently, the deformation of ceramics using nanoindentation7. He has supervised over 20 PhD students and written over 120 publications and in 1998 won the Verulam Medal and Prize for his work on layered ceramics. His research is focussed on the processing and properties of ceramics8. Since 1992 has been the principal investigator on 10 projects with a value of £7M, funded mainly by industry, the European Community and NEDO, Japan.

Other Academic Collaborators

Professors Franz Ulm and John Ochsendorf from the Departments of Civil and Environmental Engineering and Architecture respectively at MIT have expertise in durability and chemo-poro-mechanics and sustainable building materials respectively. They are submitting an independent and complementary proposal for US funding. If funded, their project will involve detailed nano-indentation studies and life cycle analyses of the manufacture of MgO cements and related products. MIT are also bringing Lafarge cement on board, a company with which they have strong links. MIT is one of the world leading academic institutions in science and engineering and are renowned for their entrepreneurial initiatives. Cambridge University and MIT have on-going research, educational and industry relevant collaborations through the Cambridge-MIT Institute, which involves frequent visits of academics between the two institutions.

TecEco Technology Pivital for the Rheology Required for Cementitious Compositites Required by our Robotic Workforce of the Future?

In the last newsletter (33) I discussed the development of robotics for construction. In this article I will go into the rehology, perceived by many as the important factor that will make the technology possible.

For robotics to be used in construction it will be necessary to squeeze self hardening materials out of a nozzle so they just sit without deformation until they gain full strength.

Various materials from structural to void filling and insulating will be required and like a colour inkjet printer will be selected as specified by the design.

Accuracy will be far greater than currently possible, wonderful architectural shapes as yet unthought of will be used and fibres will provide reinforcing. Walls will most likely only have a low strength foamed insulating cementitious material between them making services easy to add at a later time. Conduits could also be provided by design.

 

Robot Construction in the Future

The use of robots in construction will reduce the waste of new construction materials immensely. Just like an inkjet printer only uses the right amount of ink, only the exact amount of material will be used. The introduction of robots to construction will also mean more wastes can be utilised for building materials. More self hardening materials will be required, not less and mineral binders like TecEco's new cements have the obvious advantage of being able to utilise a large quantity of wastes.

The Physics of Rheology

Most fluids are adequately described by Newtons laws of viscosity and are referred to as Newtonian fluids.

Newton's law of viscosity is given by

t = m*dv/dy

where t = shear stress

m = viscosity of fluid

dv/dy = shear rate, rate of strain or velocity gradient

All gases and most liquids which have simpler molecular formula and low molecular weight such as water, benzene, ethyl alcohol, CCl4, hexane and most solutions of simple molecules are Newtonian fluids.

Non-Newtonian fluids on the other hand are fluids which do not obey the Newton's law of viscosity. They are generally complex fluid mixtures such as slurries, pastes, gels, polymer solutions etc.

There are various Newtonian and non-Newtonian behaviours as in the graph below.

Newtonian and Non-Newtonian Behaviours

Consider the behaviours depicted in the graph

Time-Independent behaviours:

Properties are independent of time under shear.

Bingham-plastic:

Resist a small shear stress but flow easily under larger shear stresses. e.g. tooth-paste, jellies, and some slurries.

Some TecEco cements have some Bingham plastic behaviour characteristics and will be important to provide the rheology required for the robotic construction of buildings and other structures.

We need to initiate research projects looking into suitable rheology modifiers. Anybody out there interested in funding this?

Pseudo-plastic:

Most non-Newtonian fluids fall into this group. Viscosity decreases with increasing velocity gradient. e.g. polymer solutions, blood. Pseudoplastic fluids are also described as shear thinning fluids. At low shear rates(du/dy) the shear thinning fluid is more viscous than the Newtonian fluid, and at high shear rates it is less viscous.

Dilatant fluids:

Viscosity increases with increasing velocity gradient. They are uncommon, but suspensions of starch and sand behave in this way. Dilatant fluids are also called shear thickening fluids.

Time dependent behaviours:

Time dependent fluids are fluids that are dependent upon duration of shear.

Thixotropic fluids

Are fluids for which the dynamic viscosity decreases with the time for which shearing forces are applied. e.g. thixotropic jelly paints.

Rheopectic fluids

With rheopectic fluids dynamic viscosity increases with the time for which shearing forces are applied. e.g. gypsum suspension in water.

Visco-elastic fluids

Some fluids have elastic properties, which allow them to spring back when a shear force is released. e.g. egg white.

Way to go may be Tec Cements for Blocks

So far Tec-Cement concretes are developing 30 - 40% more strength than the equivalent PC formulations so sustainability is achieved by using less binder. Because of scale problems it is not yet economic to use Eco-Cement for block making so we are focussing on testing Tec-Cements for difficult to make masonry units and for added strength and binding with lightweight blocks.

New Important Paper for Download

A new paper is available for download on the web. As I feel strongly about the importance of materials in making reducing, reusing and recycling economic I suggest all those interested read the paper.

It is available at www.teceo.com/Sustainability_Documents/MakingRecyclingEconomicShortSustainableWasteManagement&RecyclingKingstonUK150904.pdf

Making Recyling Economic – The Sustainability Of Materials For The Built Environment

A John W Harrison, B.Sc. B.Ec. FCPA.
Managing Director and Chairman, TecEco Pty. Ltd.
497 Main Road, Glenorchy TAS 7010. Australia.

Our interaction with our planet earth is described as the techno-process which is the process of taking resources, manipulating them as required (modifying substances), making something with them, using what is made and then throwing what has been made that no longer has utility away. The techno-process of take, manipulate, make, use and waste is discussed particularly in relation to reducing, reusing and recycling materials, earth systems, the web of life and materials in the built environment which, at over 70% of all materials flows, comprise the major component of the flow through the techno process. The most significant material flow is that of concrete as over two tonnes are produced per person on the planet per annum. The use of new calcium magnesium blended cements (TecEco cements) invented by the author that utilise wastes and sequester carbon dioxide is discussed as an example of the significant impact improvements in materials could make.

Reducing, re-using and recycling materials would reduce the impact of the techno process on the planet, but is currently undertaken more for “feel good” political reasons than sound economic reasons in many instances. Some unique solutions are offered to resolve this dilemma including a unique electronic identification system for materials and the use of new generation TecEco cement composite materials as potential repositories of wastes including CO2.